A piece of stock which is cut on a workbench usually contacts a fence along one of its sides. Along its oppositely facing side, the stock contacts a guide which serves to control the movement of the stock across the working surface. The guide is usually fitted with a tongue which slides in a groove. The groove conventionally extends laterally across the working surface. By means of the tongue, the stock can travel on a path which is parallel to the groove.
Many problems are encountered in controlling the stock in this manner. For the tongue to move smoothly in the groove, it cannot be too tight-fitting. The looser it is, however, the more subject the tongue is to vibration or oscillation. Such movement causes a like movement of the guide with a resulting loss in precision of the cut made by the power tool. Such movement also causes fatigue since the operator will feel the movement when his hands are on the guide.
Another problem which is frequently encountered is that the stock tends to bind in the cutter of the power tool as the stock is being moved across the working surface. The reason is that the groove in which the tongue of the guide travels is spaced apart from the cutter a significant distance to prevent it from interfering with the cutting operation. The guide, being attached to the tongue, is spaced apart an equal distance. The further the guide is from the point at which the stock is cut, the less effective it is in preventing unintended movement of the stock at that point. Such movement is usually the cause of binding.
A further problem is that as the cutter rotates, it urges the stock away from the fence and toward the guide. Because of the significant spacing between the cutter and the guide, the stock is difficult to control and unintended movement of the stock may occur.